Download Electronics summary notes

Electronics
David Smith
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Introduction
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Electronic systems have 3 parts
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Input
Process
Output
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There are 2 types of systems:
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Analogue
Digital
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Output Devices
These turn EE into some other form
Analogue
Motor, Bulb, Loudspeaker
Digital
LED, Relay, Solenoid
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Input Devices
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2 main types
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Change the size of the input
voltage
Switch, Capacitor,
LDR, Thermistor
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and
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Input Devices
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Energy Changers
Thermocouple, Microphone
Solar Cell
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LDR
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As Light Intensity Increases
Resistance Decreases
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Thermistor
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As Temperature increases the
resistance decreases
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Capacitors
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Store Charge
V
–  t
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Provide timing delays
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Voltage Dividers
Vs
R2
VOUT = V S ×
R1 + R2
R1
R2
Vout
0V
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LDR in Voltage Divider
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As light increases, resistance of
LDR decreases, voltage across it
decreases,
V out
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Thermistor
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As temperature decreases, resistance of
thermistor increases,voltage across
thermistor increases, V out decreases
Vout
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Capacitor
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Capacitor charges up
Vout increases
Vs
V out
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Switches
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When switch is closed
V out is low
+5V
V out
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Process Devices
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Analogue : Amplifier
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Digital : Transistor
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NPN Transistor
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V be > 0.7 V
Transistor is switched on
Collector
Base
Emitter
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Alarm Circuits
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Light Intensity decreases
R ldr increases
V ldr increases
V be increases
V be > 0.7 V
Transistor switches on
Current flows through LED
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Alarm Circuits
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Temperature increases
R thermistor decreases
V thermistor decreases
V resistor increases
V be increases
V be > 0.7 V
Transistor switches on
Current flows through LED
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